1. Field of the Invention
The present invention relates to security system locks and, more particularly, to high security combination locks and cabinets, safes, vaults, doors and doors employing such locks.
2. Description of the Prior Art
Conventional security system combination locks generally include certain basic components. Such locks usually include three or four stacked tumbler wheels which are coaxially mounted for rotation about a post disposed within a lock casing. The lock dial, which usually has a plurality of calibration marks such as the numbers 1 to 100 thereon, is connected to a spindle which extends into the lock case. A drive wheel is generally provided in a coaxial relationship with the tumbler wheels for driving the tumbler wheels, drive wheel itself being driven by rotation of the lock dial.
A drive pin typically projects from the drive wheel and, conventional fly rotatable through a limited arc associated with the endmost tumbler wheel, provides a lost motion coupling to drive the endmost tumbler heel a predetermined relationship to the drive wheel. A similar lost motion coupling is generally provided between each of the successive tumbler wheels so that each of the tumbler wheels may be driven upon predetermined rotation of the drive wheel. Generally, the lost motion coupling between each of the successive tumbler wheels and between the endmost tumbler wheel and the drive wheel includes a fly having a ring portion journaled in concentric relation with its associated tumbler wheel and the ring portion having a radial projection which lies between a pair of stop shoulders formed in the tumbler wheel and disposed to limit angular rotation of the fly to a desired lost motion range, such as about 20.degree.. A drive pin or lug projects from the adjacent tumbler wheel to engage the fly and thus engage the stop shoulders of the first mentioned tumbler wheel provided the fly has moved through its predetermined lost motion angular range. Each of the tumbler wheels and the drive wheel is provided with a peripheral notch or gate at a selected radial position along the circumferential edge thereof.
A fence lever is generally pivotally connected near one end to a reciprocating bolt slidably supported in the lock casing. The fence Lever is frequently provided with a depending nose portion near the opposite or free end thereof which, in conventional combination locks, is designed to ride upon the drive wheel periphery. This nose portion usually includes a fence projecting laterally from the fence lever in overlaying relation to the peripheries of the tumbler wheels. The position of the fence in relation to the length of the fence lever nose is usually such that the fence is spaced slightly outwardly from the peripheries of the tumbler wheels when the fence lever nose is riding on the drive wheel periphery.
In the case of such conventional combination lock mechanisms, the combination lock is opened by rotation of the dial in a predetermined sequence of clockwise and counterclockwise direction through predetermined numbers of revolutions to a series of numerical positions indicated by alignment of the calibration marks on the lock dial with a fixed index. Such dialing of a predetermined series of combination numbers effects angular rotation of the plurality of tumbler wheels. This results in the alignment of the tumbler wheel peripheral gates with the fence. The dial is then rotated to bring the drive wheel gate to a position registered with the fence lever nose to cause the fence lever nose and fence to drop into the aligned gates whereupon further rotation of the dial through a partial revolution in a predetermined direction achieves retraction of the lock bolt.
During normal use of such combination locks, and in particular high security locks, it becomes necessary to change the lock combination at various times. In fact, it is standard operating procedure in many areas of business and government to change the lock combination at frequent intervals for security reason, even as often as once a day. Changes in personnel and possible unauthorized access to the combination, among other reasons, dictate such changes to the lock combination.
In conventional combination locks utilizing such rotatable tumblers as described above, the lock combination is frequently changed by hand. This requires opening the lock case, taking the tumbler mechanism apart, resetting angular position of each tumbler gate with respect to the dial, reassembling the tumblers, and replacing them in the lock case. This mode of changing the combination oftentimes requires the efforts of a locksmith and, at the very least, requires a fairly extensive amount of work for each combination change. Moreover, the loss of a small part or the mishandling of component portions can cause further difficulties. On the other hand, this type of lock combination changing mode permits the maximum number of possible lock combinations to be selected.
Combination locks which include tumblers having externally actuated mechanisms for effecting the resetting of the combination through means of a special tool or key have also been provided in the past. U.S. Pat. No. 3,386,275 is one example of such a mechanism. Such key changeable tumbler mechanisms are usually actuated by a key which is inserted through an aperture provided in the rear wall of the lock case. The key uncouples an outer tumbler gate portion from an inner tumbler portion, thereby permitting the angular position of the dial relative to one or more of the tumbler gate portions to be changed without disassembling the lock.
While such key changeable tumblers do afford convenience to the operator, they have frequently been lacking in many other respects. In particular, key changeable tumbler constructions have been subject to attack by radiographic means whereby the tumbler gate positions can sometimes be determined through X-ray photographs of the lock taken through the safe or file. Other proposed constructions have not afforded sufficiently positive mechanisms for determining or holding the preselected position of the various adjustable tumbler portion with the result that undesirable relative movement of the tumbler gates sometimes occurs. This makes these constructions more readily subject to unauthorized external access.
Prior combination locks have also been provided with various types of mechanisms mounted on the drive wheel to resist detection of the "feel" of the points of engagement of the fence lever nose with the driving wheel gate in accordance with well-known lock manipulation procedures. One such example is U.S. Pat. No. 3,968,667 wherein the fence lever is maintained away from the driver wheel and tumblers by a spring loading mechanism. Frequently, however, such mechanisms have complicated the construction of the locks as well as been only partially effective in shielding the lock mechanism from external detection.